The transmission system, containing over 32,000 kilometres (20,000 mi) of power lines, is managed by Hydro-Québec TransÉnergie, a division of the crown corporation Hydro-Québec. One unique feature of the power system is its alternating current (AC) 735 / 765 kV power lines that stretch from the population centers of Montreal and Quebec City to the distant hydroelectric dams and power stations of the James Bay Project and Churchill Falls. The 735 kV power lines serve as the main backbone of the entire transmission system, and thus much of Quebec's population is powered by a handful of 735 kV power lines. This contributed to the severity of the blackout that ensued after the Ice Storm of 1998. The extent and duration of this blackout has generated criticism of the transmission system, and there is controversy concerning the use of hydroelectric dams.
Quebec's power transmission history began with the inauguration of a -long, 50 kV power line running from Shawinigan to Montreal. At that time, regional monopolies dominated the Quebec electricity market. In light of customer complaints, the Quebec government expropriated all power companies into Hydro-Québec on April 14, 1944.
Planning for Hydro-Québec's 735 kV power grid began in 1955, when engineers looked to transmit 5,000 megawatts (MW) hydroelectric power from the Manicouagan-Outardes (Manic-Outardes) dams to Montreal, a distance of . At that time, by using the world standard 300–400 kV voltage level, this feat would have required at least 30 individual power lines. Initially, a voltage level of 500 kV was chosen to transmit electric power, but 500 kV was considered to be a small improvement over the existing voltage level of 315 kV.
To effectively resolve this issue, Jean-Jacques Archambault, now regarded as the pioneer of the 735 kV power line, decided on a voltage level of 735 kV, a level over twice as high as the previous 315 kV. In 1962, Hydro-Québec proceeded with the construction of the first 735 kV power line in the world. The line, stretching from the Manic-Outardes dam to the Levis substation, was brought into service on November 29, 1965 at 1:43 pm.
Over the next twenty years, from 1965 to 1985, Quebec underwent a massive expansion of its 735 kV power grid and its hydroelectric generating capacity. Hydro-Québec Équipement, another division of Hydro-Québec, and Société d’énergie de la Baie James built these transmission lines, electrical substations, and generating stations. Constructing the transmission system for the La Grande Phase One, part of the James Bay Project, took 12,500 electrical pylons, 13 electrical substations, of ground wire, and of electrical conductor at a cost of C$3.1 billion alone. In less than four decades, Hydro-Québec's generating capacity went from 3,000 MW in 1963 to nearly 33,000 MW in 2002, with 25,000 MW of that power sent to population centers on 735 kV power lines.
The James Bay Project encompasses the La Grande project, which is located on the La Grande River and on its tributaries, such as the Eastmain River, in northwestern Quebec. The La Grande project was built in two phases; the first phase lasted twelve years from 1973 to 1985 and the second phase lasted from 1985 to present time. In all, the nine hydroelectric dams there produce over 16,500 MW of electric power, with the Robert-Bourassa or La Grande-2 station generating over 5,600 MW alone. In total, the project cost over C$20 billion to construct.Manic-Outardes power stations The Manic-Outardes river area in the Côte-Nord or North Shore region consists of several hydroelectric facilities located on three principal rivers, from west to east: Rivière Bersimis, Rivière aux Outardes, and the Manicouagan River. A single plant named Sainte-Marguerite-3 is located to the east on the Rivière Sainte-Marguerite. The facilities located in the region were constructed over a period of five decades, from 1956 to 2005. The total generation capacity from these power stations is 10,500 MW. A small generation plant located on the Rivière Ha! Ha! is not connected to the Quebec grid.Churchill Falls Churchill Falls is a single underground generation station located on the Churchill River near the town of Churchill Falls and the Smallwood Reservoir in Labrador. It was constructed over a period of five to six years from 1966 to 1971–72 by the Churchill Falls (Labrador) Corporation, though generators were installed after major construction was completed. The single generation facility cost C$946 million to construct and produced 5,225 MW of power initially after all eleven generating units were installed. A station upgrade in 1985 raised the generating capacity to over 5,400 MW. The station is not owned by Hydro-Québec Generation, but instead by the Churchill Falls (Labrador) Corporation, which is the same company that constructed the generating plant. However, Hydro-Québec has rights to most of the 5,400 MW of power the station produces.
The physical size of the Hydro-Québec's 735 kV transmission lines is unmatched in North America. Only two other utility companies in the same region, the New York Power Authority (NYPA) and the American Electric Power (AEP) contain at least one 765 kV line in their power system. However, only AEP has a significant mileage of 765 kV power lines, with over of 765 kV line traversing its broad transmission system; this system contains the most mileage in the United States under one electrical company. NYPA has only of 765 kV line, all of it contained in a single direct interconnection with Hydro-Québec.
The 735 kV power line is said to lessen the environmental impact of power lines, as one single power line operating at this voltage carries the same amount of electric power as four 315 kV power lines, which would require a right-of-way wider than the – width required for a single 735 kV line. Each 735 kV line is capable of transmitting 2,000 MW of electric power at a distance of over 1,000 kilometres (600 mi) and the entire 735 kV grid can carry 25,000 MW of power. Power transmission losses over the 735 kV grid range from 4.5 to 8%, varying due to temperature and operating situations. The Ordre des ingénieurs du Québec named the 735 kV power line system as the technological innovation of the 20th century for Quebec.
As the lines continue south, they diverge into two sets of three 735 kV transmission lines. The eastern set heads to Quebec City, where it connects with power lines from Churchill Falls and the 735 kV power line loops in the Saint Lawrence River region. The western set heads to Montreal, where it too forms a ring of 735 kV power lines around the city, linking to other power loops in the region. This section of Hydro-Québec TransÉnergie's power grid contains of AC 735 kV and DC ±450 kV power line.Manic-Outardes power stations / Churchill Falls
Electrical power generated from the Churchill Falls power station is sent to Montreal and the population centers of the Northeastern United States, more than away. Starting from the generation station in Labrador, the power lines span a distance of over the Churchill River gorge and run generally south-southwest for as three side-by-side power lines in a cleared right-of-way with a width of 216 metres (710 ft). As they head southwest through boreal forest, the lines generally traverse flat, smooth rolling hills.
After the lines cross the Quebec-Labrador border, also known as the Hydro-Québec point of delivery, the direction of the lines becomes due south, and they head into a substation adjacent to the Poste Montagnais (Mile 134) Airport. A lone 735 kV line stems off from the substation, heading to an open pit mine far to the northwest. The terrain crossed by the power lines becomes hilly and mountainous south of the border. The lines reach over in elevation before descending. The three lines continue heading south until they reach a substation on the North Shore of the Gulf of Saint Lawrence. From there on, the three lines parallel the North Shore as the Gulf narrows to the southwest toward the Saint Lawrence River discharge mouth. The northernmost power line then diverges from the other two to connect with Manic-Outardes power stations located on and around the Rivière aux Outardes and the Manicouagan River.
As the lines near Quebec City, the northern power line rejoins the other two 735 kV power lines. The three lines, paralleled by another 735 kV power line some distance to the north, span over the Saint Lawrence River to the South Shore region, where the lines form loops encompassing part of the Saint Lawrence River and the south shore. The loops are also connected to the ring of 735 kV power lines around Montreal and power lines running south from James Bay.
Hydro-Québec TransÉnergie uses several different types of electricity pylons to support their 735 kV power lines. All of them are single-circuit, meaning that each pylon carries one power line with three bundles of four electrical subconductors separated by spacers, with each bundle transmitting one phase of current.
The earliest type of tower used was a massive self-supporting delta pylon, or waist pylon, which consumed 21 tonnes of steel per kilometre of line. This type of pylon was used for the first 735 kV power line from the Manic-Outardes power stations to the load centre of Montreal. There are two significant variations of the delta pylon; one has longer side crossbars such that all three bundles of conductors are suspended on V-shaped insulators. The other has shorter side crossbars, such that the two outside bundles are hung on a vertical insulator string and only the middle bundle is hung with a V-shaped insulator.
Over the years, Hydro-Québec researchers engineered a new type of pylon, the V-guyed tower, which reduced materials consumption to 11.8 tonnes of steel per kilometre of power line. This type of tower also includes a variation with longer side crossbars, where all conductors are hung with a V-shaped insulator and one with shorter side crossbar, where only the middle bundle hangs from the insulator and the side bundles are strung on vertical insulator strings.
During the construction of the James Bay transmission system, the cross-rope suspension tower was invented. This type of tower features two guyed-tower legs similar to the V-guyed tower, but the two legs don't converge at the tower base. In the case of the cross-rope suspension tower, the tower legs are spread apart on two different foundations. In addition, the crossbar is replaced by a series of suspension cables with three vertical insulator strings to support the three bundles, which allows this design to consume only 6.3 tonnes of steel per kilometre of line. The design is also known as the Chainette (little necklace).
TransÉnergie uses two-level pylons for angle towers or structures on 735 kV power lines to change the direction of the line or switch the position of the conductor bundles. Delta pylons and three-leg guyed towers are also used as angle towers; they are referred to as "penguins" by Hydro-Québec linemen.Pylons for other voltage levels Hydro-Québec TransÉnergie uses a combination of double-circuit three-level pylons and single-circuit delta pylons to suspend electrical conductors of other voltages, such as 315 kV. The ±450 kV high-voltage direct current line in Hydro-Québec's power grid uses a T-shaped tower, lattice or pole, to support two bundles of three conductors on each side. The direct current power line sometimes uses two poles or a wider, pyramidal, self-supporting lattice structure for angle towers.Other plyons Hydro-Québec usually uses tall, large pylons to cross large bodies of water, like lakes and rivers. These towers are said to be prominent and the tallest pylon in Hydro-Québec's power grid is of this function. It is located near the Tracy power station on the shore of the Saint Lawrence River between Berthierville and Tracy. The pylon is tall, the same height as the Montreal Olympic Stadium.Pylon strength The pylons and conductors are designed to handle 45 millimetres (1.8 in) of ice accumulation without failure, since Hydro-Québec raised the standards in response to ice storms in Ottawa in December 1986 and Montreal in February 1961, which left 30 to 40 millimetres (1.2 to 1.6 in) of ice. This has led to the belief that Hydro-Québec TransÉnergie's electrical pylons are "indestructible". Despite being more than three times higher than the Canadian standard of only 13 millimetres (0.5 in) of ice tolerance, an ice storm in the late-1990s deposited well over 45 millimetres (1.8 in) of ice.
After the six 735 kV wires split up into two groups of three power lines each, the HVDC line follows the eastern group, and the western set diverges away. The line remains overhead until it reaches the north shore of the Saint Lawrence River near Grondines, where the ±450 kV HVDC line descends into an underwater tunnel traversing the river. The crossing was the world's first underwater crossing for a ±450 kV HVDC line. The power line surfaces on the south shore near Lotbinière substation. After the river crossing, the line enters into the Nicolet terminal near Montreal. South of the terminal, the line heads south and after a relatively short distance, it enters the Des Cantons close to Sherbrooke.
Leaving the Des Cantons station, the power line crosses the United States-Canada border and passes through the hilly Appalachian Mountains in the U.S. state of Vermont, reaching an elevation of about . The line then continues heading south-southeast and enters the state of New Hampshire, where it reaches the Comerford terminal near Monroe. Continuing southward into Massachusetts, the line reaches the Sandy Pond terminal outside of Boston in Ayer. The terminal is the southernmost extent of the HVDC line.
Accordingly, protective measures were taken in response. To save the transformers and other electrical equipment, the power grid was taken out of commission, as circuit breakers tripped all over Quebec and shut off the power. Within less than 90 seconds, this wave of breaking circuits left the entire transmission grid out of service. The collapsed power grid left six million people and the rest of Quebec without electricity for hours on a very cold night. Even though the blackout lasted around nine hours for most places, some locations were in the dark for days. This geomagnetic storm caused about C$10 million in damage to Hydro-Québec and tens of millions to the customers of the utility.
From January 4/5 to January 10, 1998, warm moist air from the south overriding cold air from the north produced an ice storm, leading to over 80 hours of freezing rain and drizzle. For days, a continuous shower of mostly freezing rain amounted to 70–110 millmetres (2.8–4.3 in) of water equivalent of precipitation. Places like Montreal and the South Shore were especially hard hit, with of largely freezing rain falling. These heavy precipitation totals wreaked havoc on the regional power transmission system.Physical damage Five to six days of freezing rain and precipitation crippled the Hydro-Québec power grid in the Montreal and South Shore regions. In an area 100 by 250 kilometres (60 by 150 mi), some 116 transmission lines were out of commission, including several major 735 kV power lines and the Quebec–New England HVDC ±450 kV line. Through successive waves of freezing precipitation, more than 75 millimetres (3.0 in) of radial ice accumulated on the electrical conductors and the pylons themselves. This ice coating adds an additional weight of 15 to 20 kilograms per metre of conductor (10 to 20 lb/ft). Even though the electrical wires can withstand this extra weight, when combined with the effects of wind and precipitation, these conductors may break and fall. The pylons, designed to withstand only 45 millimetres (1.8 in) of ice accretion, buckled and collapsed into twisted heaps of mangled steel. Cascading failures occurred on several transmission lines, where the collapse of one or more towers left a row of fallen pylons.
Of all the pylons damaged, some 150 were pylons supporting 735 kV lines, and 200 towers carrying 315 kV, 230 kV, or 120 kV power lines collapsed as well. In a region bounded by Montreal between Saint-Hyacinthe, Saint-Jean-sur-Richelieu and Granby, dubbed the "triangle of darkness", half of the overhead power grid was out of service. Quebec ordered myriad conductors, crossarms, and wire connections to repair the ones disabled by the storm in the electrical transmission and distribution system. In all of Quebec, 24,000 poles, 4,000 transformers, and 1,000 electrical pylons were damaged or destroyed, more than of downed electrical wires; this cost a total of C$800 million to repair.Power outage With over 100 transmission lines paralyzed by the ice, Quebec fell into a massive power outage in the cold Canadian winter. Even though power restoration initiated after the first blackouts, large numbers of Quebecers were in the dark. At the height of the blackout, some 1.4–1.5 million homes and customers, housing three to more than four million people, were in the dark. Private companies and other utilities from other parts of Canada and the United States were sent in to help Hydro-Québec undertake this massive restoration task, but these efforts were complicated by the widespread damage of the power grid. Blackouts in some areas lasted for 33 days, and 90% of those affected by the blackout had no power for more than seven days. Although power was fully restored to all locations in Quebec by February 8, 1998, it wasn't until mid-March that the power facilities were back in service. By then, much social and economic damage had occurred, such as ruined food and deaths resulting from lack of electric heating.
After the power outage was over, Hydro-Québec made numerous upgrades to its system in order to improve the power grid. Examples include the strengthening of electrical pylons and power poles, and increasing the power supply. This was done to enable the utility to restore power more rapidly in the case of a massive ice striking Quebec again. Hydro-Québec has stated that it is better-prepared to handle an ice storm with the same magnitude as the one of 1998.
The technology utilized on Hydro-Québec TransÉnergie grid also came under fire from critics. It is claimed that this technology, used to improve performance, safety, and reliability, made people in Quebec over-dependent on the power grid for their energy needs, since electricity, especially hydroelectric power, makes up over 40% of Quebec's energy supply. This dependence, evidenced by the fact Ontario farmers had more backup generators than farmers in Quebec, can increase the severity of the consequences when the grid fails, as it did in January 1998.
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